Covalent Functionalization of the 2D C₆₀ Network via Aryl Diazonium Chemistry Enables Visible-Light-Driven Ammonia Synthesis

Photocatalytic nitrogen reduction offers a sustainable approach to ammonia production. Here, we develop covalently functionalized 2D fullerene (C60) networks through aryl diazonium chemistry, as verified by neutron scattering, spectroscopic analysis, and atomic force microscopy (AFM). The functionalized 2D fullerenes (e.g., with 4-nitrophenyl and 4-methoxyphenyl groups) demonstrate notable nitrogen reduction activity under visible light irradiation, achieving significant ammonia yields without requiring any sacrificial reagents. Functionalization induces structural and electronic modifications that alter band structures and narrow bandgaps, thereby enhancing photocatalytic efficiency. Femtosecond transient absorption spectra and photoelectrochemical tests reveal prolonged electron lifetimes and suppressed charge recombination, which are critical for enhanced performance. In situ DRIFTS analysis verifies an alternating hydrogenation pathway for N2 reduction on 4-NBD/2D C60 surfaces. This work demonstrated covalent functionalization as an effective strategy to engineer 2D fullerene materials for sustainable catalytic applications, with particular promise for photocatalytic nitrogen fixation.